Thompson makes a lot of different bullets and sabots for their rifles. Cabela's has a few of them in there. Fox Ridge has a store inside the Cabela's store, and does most of their custom work. The people there have always been very helpful, and knowledgable of Thompson rifles. They can probably tell you what you want to know about your particular rifle.
Personnaly I'm shotting a 50 caliber Encore, and using 100 grains of 777, with a Thompson T/C XTP MAG Sabot (black) and a .44 magnum 250 grain Hornady Jacketed hollow point bullet.
Ask Fox ridge about buying the sabots in a bulk pack of 50 sabots, and you can get the bullets (100 to a box) from your local gun shop. This will make your expense a lot less than buying them 10 at a time.
I buy 50 sabots for about $8.00 and 1/2 box of bullets for 7.00. This gives me $15.00 for 50 rounds. What you are shooting is probably costing you about$17.00 for 30 rounds.
I don't particularly care for any of the polymer pointed or belted bullets, since the velocity of a muzzle loader isn't going to be enough for them to really make a difference at 100 yards, which is the majority of my shooting. The set up I am using will drive "same hole" groups at 50 yards and shoot 1 1/2" groups at 100 yards. I tried the shockwave bullets, but they really don't shoot any more accurate than what I am shooting now. I think the polymer tip on muzzle loader bullets is really more about making money than being any more accurate. Some of the guys here hunted with them last year and did not like the way they expanded on deer, so I have never hunted with them.
My rifle is designed to be 150 grain shooter, but will really only shoot about 130 grains with any real accuracy, and the velocity of 150 grains of 777 might be enough to give you about 2100 FPS which would still not be fast enough to make much difference in the bullets performance over the hollow points I'm shooting now, so I don't see any reason to put up with the extra re-coil for deer.